FIG 1.
Erfed/ed mice are embryonic lethal and appear anemic. (A) Pregnant mice were sacrificed at the indicated day of gestation, and the genotypes of the embryos were analyzed. The graph indicates the percentages of live Erfed/ed embryos. The data are from 160 litters, with at least 5 litters for each gestation stage (see Table S1 in the supplemental material). A chi-square test showed a statistically important decrease with the expected Mendelian distribution after E13.5. (B) Representative microphotographs of embryos at E13.5 showing apparent anemia and a lack of other gross morphology differences between Erfed/ed embryos and their ErfloxP/+ littermates. (C) Number of blood cells from the yolk sac and embryo proper at the indicated day of gestation. Erfed/ed embryos exhibit a statistically significant decrease throughout E9.5 to E13.5, which is exacerbated at E14.5. Samples are represented in a logarithmic scale. All values are means ± SE from 35 litters with at least 7 litters for each gestation stage (Table S2). Statistical analysis was performed using an unpaired t test with two-tailed distribution. *, P < 0.05; **, P < 0.005; ***, P < 0.0005, for results with ErfloxP/+ mice versus those with Erfed/ed mice.